An /fp:precise build returned the identical 454 samples, identical max delta,
identical coordinate. A different float model producing byte-identical output is
proof that rounding is not the cause, so the /fp:fast explanation is dead. That
is three failed hypotheses on one discrepancy (FVector round-trip, then "check
the roughness window", then /fp:fast), each reasoned from plausibility and each
costing a build.
So: stop reasoning, print. FVoxelOpStack::EvalSample exposes the full sample, and
MazeEquivalence now dumps the worst point in raw hex -- both densities, the
stack's internal SDF, and the carve factor reconstructed from each side. The
recovered carve localises it: identical carve + differing density means the fault
is after the conversion; differing carve means it is in the SDF (lattice edges or
VoxelSDF::Capsule) or in SmoothStep01.
Note for whoever reads the docs next: AUDIT C9 and OPSTACK-PLAN 2.6 currently
assert the /fp:fast story as the explanation for THIS residue. That specific
claim is falsified and needs walking back once the dump identifies the real
cause. C9's other half -- that UBT's FP default differs by toolchain and the MP
model assumes bit-reproducible terrain -- stands independently; it was read out
of VCToolChain.cs and ClangToolChain.cs, not inferred from this test.
Phase 1 step 3 (wiring the stack into GetDensityAt) is paused until this is
understood. Small unexplained numeric differences do not get smaller when you
build on top of them.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Fr0zka
cca9e83182